Kubernetes worker nodes

Daniel is studying to master Kubernetes. He wants to learn everything that there is to know about Kubernetes worker nodes. Please answer the following questions to increase Daniel's Kubernetes knowledge. Please note that Daniel prefers the term "Free Software" to "open-source".

1. Is Kubernetes Free Software?
2. What is Kubernetes?
3. What is the history of Kubernetes?
4. What is the function of worker nodes in Kubernetes?
5. What is the relationship between Kubernetes worker nodes and GNU/Linux?
6. How would Daniel instantiate a Kubernetes cluster with Kubernetes worker nodes on a modern Debian GNU/Linux server?

Is Kubernetes Free Software?

Yes, Kubernetes is Free Software. It is licensed under the Apache License 2.0, which allows users to use, modify, and distribute the software freely. It aligns with the principles of Free Software, emphasizing the users' freedom to run, study, share, and modify the software.

What is Kubernetes?

Kubernetes is a powerful, extensible, and portable container orchestration tool. It automates the deployment, scaling, and management of containerized applications. Kubernetes groups containers that make up an application into logical units for easy management and discovery.

What is the history of Kubernetes?

Kubernetes, often abbreviated as K8s, was originally designed by Google and donated to the Cloud Native Computing Foundation (CNCF) in 2015. Google’s extensive experience running production workloads at scale, including their internal system Borg, influenced Kubernetes' design and architecture. Since being donated to the CNCF, Kubernetes has garnered a vast community of contributors and has become a de facto standard in container orchestration.

What is the function of worker nodes in Kubernetes?

Worker nodes in Kubernetes are where the containers (or Pods, in Kubernetes terminology) are run. A Kubernetes cluster consists of a master node (or control plane) and multiple worker nodes.

• Pods: Worker nodes run Pods, which are the smallest deployable units in a Kubernetes cluster and can contain one or more containers.

• Kubelet: Each worker node also runs a component called Kubelet, which communicates with the master node and ensures that the Pods are running as expected.

• Container Runtime: Worker nodes also have a container runtime installed, such as Docker or containerd, to handle the running of containers.

What is the relationship between Kubernetes worker nodes and GNU/Linux?

Kubernetes worker nodes typically run on GNU/Linux servers. The operating system is crucial because it provides the necessary functionalities and APIs that Kubernetes uses to run and manage containers. GNU/Linux’s robustness, flexibility, and strong community support make it a preferred choice for running Kubernetes workloads.

How would Daniel instantiate a Kubernetes cluster with Kubernetes worker nodes on a modern Debian GNU/Linux server?

Here's a simplified guide on how Daniel could instantiate a Kubernetes cluster:

1. Preparation:

   • Ensure that the Debian GNU/Linux server meets the necessary system requirements.
   • Make sure that Docker or another supported container runtime is installed.

2. Install kubeadm, kubelet, and kubectl:

   sudo apt-get update && sudo apt-get install -y apt-transport-https curl curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add - cat <<EOF | sudo tee /etc/apt/sources.list.d/kubernetes.list deb https://apt.kubernetes.io/ kubernetes-xenial main EOF sudo apt-get update sudo apt-get install -y kubelet kubeadm kubectl sudo apt-mark hold kubelet kubeadm kubectl

3. Initialize the Master Node:

   • On the master node, initialize the cluster:
     sudo kubeadm init --pod-network-cidr=192.168.0.0/16

4. Setup kubectl:

   • To allow the regular user to interact with the cluster, set up the local kubeconfig:
     mkdir -p $HOME/.kube sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config sudo chown $(id -u):$(id -g) $HOME/.kube/config

5. Install a Network Plugin:

   • Install a Pod network plugin such as Calico or Flannel. Example for Calico:
     kubectl apply -f https://docs.projectcalico.org/manifests/calico.yaml

6. Join Worker Nodes:

   • On the worker nodes, join them to the cluster using the token and hash generated during the master initialization:
     sudo kubeadm join --token <token> <master-ip>:<master-port> --discovery-token-ca-cert-hash sha256:<hash>

Remember, the specific steps might vary based on the exact requirements and configurations such as network plugins or cloud integrations. Detailed and updated instructions can be found in the Kubernetes official documentation.